Lecture4_py………"………………………………………………..…………..

Python

1. Dictionary in Python
Dictionaries are used to store data values in key:value pairs
“key” : value
They are unordered, mutable(changeable) & don’t allow duplicate keys
dict[”name”], dict[”cgpa”], dict[”marks”]
dict[”key”] = “value” #to assign or add newApna College

2. Dictionary in Python
Nested Dictionaries
student[”score”][”math”]Apna College

3. Dictionary Methods
myDict.keys( ) #returns all keys
myDict.items( ) #returns all (key, val) pairs as tuples
myDict.update( newDict ) #inserts the specified items to the dictionary
myDict.values( ) #returns all values
myDict.get( “key““ ) #returns the key according to value Apna College

4. Set in Python
Set is the collection of the unordered items.
Each element in the set must be unique & immutable.
null_set = set( ) #empty set syntax
nums = { 1, 2, 3, 4 }
set2 = { 1, 2, 2, 2 }
#repeated elements stored only once, so it resolved to {1, 2}Apna College

5. Set Methods
set.add( el ) #adds an element
set.remove( el ) #removes the elem an
set.clear( ) #empties the set
set.pop( ) #removes a random value Apna College

6. set.union( set2 ) #combines both set values & returns new
set.intersection( set2 ) #combines common values & returns new
Set MethodsApna College

7. Let‘s Practice
Store following word meanings in a python dictionary :
You are given a list of subjects for students. Assume one classroom is required for 1
subject. How many classrooms are needed by all students.
”python”, “java”, “C++”, “python”, “javascript”,
“java”, “python”, “java”, “C++”, “C”
table : “a piece of furniture”, “list of facts & figures”
cat : “a small animal”Apna College

8. Let‘s Practice
WAP to enter marks of 3 subjects from the user and store them in a dictionary. Start with
an empty dictionary & add one by one. Use subject name as key & marks as value.
Figure out a way to store 9 & 9.0 as separate values in the set.
(You can take help of built-in data types) Apna College